1. Field of the Invention
The invention concerns personal care compositions having excellent moisturization coupled with undiminished skinfeel properties.
2. The Related Art
Dry skin is a problem in varying degree to most humans. This condition is particularly evident in winter. Personal care products such as skin creams/lotions, shampoos/conditioners, toilette bars/shower gels and antiperspirants/deodorants are normally formulated with at least one material to address dry skin. Symptoms such as itching, flaking and a visually displeasing dermal appearance can all to some extent be modulated.
There are three traditional classes of materials employed against the problem. Occlusives such as petrolatum or silicone oils serve to inhibit loss of natural moisture. They form a barrier between the epidermis and the environment. Another approach is the use of keratolytic agents to enhance rate of dermal exfoliation. Alpha-hydroxy acids are the most common agents for achieving exfoliation.
A third approach to dry skin is topical application of humectants. Hydroxylated monomeric and polymeric organic substances are generally used for this purpose. Glycerin known also as glycerol is one of the most effective humectants.
Quaternary ammonium compounds have recently been commercialized as moisturizers. One of these known under the trademark Honeyquat 50 with INCI name of Hydroxypropyltrimonium Honey has been reported to be a better humectant than glycerin at levels of 2%. See the Arch/Brooks brochure titled “Cosmetic Ingredients & Ideas®”, Issue No. 2, August 2001. Honeyquat 50 is described as being derived from the reaction of pendent hydroxyl groups (on the disaccharide) of a “light” deodorized grade of honey with a chlorohydroxytrimethylammonium derivative. Another commercial quaternary ammonium moisturizer is Cola™Moist 200 with INCI name of Hydroxypropyl Bis-Hydroxyethyldimonium Chloride. See the Colonial Chemical Inc. brochure titled “Cola™Moist 200”, copyright 2004. U.S. Pat. No. 6,869,977 B1 (O'Lenick, Jr. et al.) to Colonial Chemical Inc. discloses a related monocationic material described as a moisturizing agent.
There are several shortcomings in the performance of known humectants. Even the best such as glycerin requires to be formulated at relatively high levels to achieve good moisturization. Very high levels interfere with formulation space, result in poor skinfeel and engender incompatibility with other ingredients.
Accordingly, the present invention seeks to retain the special humectancy of glycerin seen at high concentration levels in a system featuring lower levels that minimize the disadvantages of glycerin.